Early HIV diagnosis is critical for prevention of new HIV infections. Diagnosed patients can limit further transmission and receive medical care that reduces infectivity. Two effective approaches are "population-based screening" and "transmission network targeting." In healthcare settings, population-based screening is emphasized as a means to test all persons in a defined population, but the vast majority of tests will be negative. In public health and HIV care settings, targeting of transmission networks by testing exposed partners or peer-recruited social contacts is emphasized. This efficiently identifies undiagnosed individuals with fewer negative tests, but misses others not known to be network members. Scarce resources prevent full implementation of either approach, yet partial implementation of multiple complementary and intersecting strategies might be more effective and feasible than full implementation of any one strategy. Demonstrating the implementation and outcomes of such a multi-component screening approach could lead to coordinated allocation of resources on a system-wide basis for maximal impact. The goal of this innovative implementation research proposal is to test whether combinations of screening methods improve the early detection of undiagnosed HIV. We will use population-based screening to identify infected or at-risk patients and then target the transmission networks rendered accessible by those patients. Our emergency department (ED) HIV screening program identifies patients who are: 1) HIV negative but high-risk, 2) known to be HIV positive and engaging in high-risk behavior, and 3) newly diagnosed in the ED as HIV positive. Patients will be asked to provide access to transmission networks. We will then implement an array of multi-component transmission network targeting "packages" in three complementary settings: the ED itself, our HIV treatment center, and our local health department. Package components will focus on: companions present with patients when care is delivered, peer-referral for testing, and health department partner notification. Our specific aims are to measure changes in: 1) number newly diagnosed as a proportion of total tests, and 2) early diagnosis as indicated by median initial CD4 count, that result when we augment an existing population-based ED screening program with comprehensive system-wide transmission network targeting. We will directly characterize the interrelatedness of package components and their capacity to augment one another. By integrating complementary strategies within and across settings, we will inform health policy, promote translation of screening to practice, and demonstrate a means to improve early diagnosis of HIV. PUBLIC HEALTH RELEVANCE: Earlier diagnosis of HIV is critical for prevention. We have effective strategies, but implementation is incomplete. Translation of population-based screening and transmission network targeting in both public health and healthcare settings could be accelerated by a better understanding of the beneficial outcomes of available strategies relative to one another. The fundamental contribution of this study will be to measure the impact of an integrated system-wide approach using the combination of population-based screening and transmission network targeting in public health and healthcare settings.